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(No Model.)

S. J. LARNED & P. A. PICKBRNELL. STATION APPARATUS FOR TELEPHONE GIRGUITS.

No. 501,086. Patented July 11, 1-893.

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UNITED STATES PATENT OFFICE.

SHERWOOD J. LARNED, OF EVANSTON, ILLINOIS, AND FRANK A. PIOKER- NELL, OF NEWARK, NEW JERSEY, ASSIGNORS TO THE AMERICAN TELE- -PHONE AND TELEGRAPH COMPANY, OF NEW YORK.

STATION APPARATUS FOR TELEPHONE-CIRCUITS.

SPECIFI ATION forming part of Letters Patent No. 501,086, dated July 11, 1893, Application filed March 20, 1893. Serial No. 466,868. (No model.)

To aZZ whom it may concern:

Be it known that we, SHERWOOD J. LARNED, residing at Evanston, in the county of Cook and State of Illinois, and FRANK A. 'PIGKER- NELL, residing at Newark, in the county of Essex and State of New Jersey, have invented certain Improvementsin Station Apparatus for Telephone-Circuits, of which the following is a specification.

to This invention relates to that class of telephone exchange systems in which a series of stations are served by a smaller number of main circuits, which however are common to and accessible by all stations of the series, I 5 and which all extend from all substations to a central station. In such an exchange there is great economy in the mainline conductors; while by reason of the fact that each substation has a number of main lines leading to the central office, there is a reasonable expectation, though each line is capable of being used by any substation in the system, that g each substation desiring communication, will always find a conductor free and at its disposal. In two other applications, filed of even date herewith, respectively by Frank A. Pickernell, and by ourselves are described and claimed, in the first apparatus and circuit arrangements whereby in such a system, the 0 substation may at any time send a call signal to the central office indicating that communication is desired, and whereby the said substation, or its correspondent, may be enabled at the close of said communication to apprise 3 5 the central station of the fact and thus indicate the necessity of disconnection; and in the second apparatus and circuits whereby in such a system as has been outlined, the substation may be able to distinguish among the lines accessible thereto, the lines in use from the free lines or the lines not in use, and thus to prevent the connection of any second telephone to a line already in use.

This invention relates to apparatus and cir- 5 cuits embodying the essential features shown in the two applications referred to, and has special reference to a secrecy device connected in each main line atthe several substations, by means of which, when any main line is connected for useat any substation, it is impossible for any other substation to connect with the same main line, thus insuring absolute secrecy to the connecting substation. We

also combine the line in use or busy visual signal, forming the subject matter of. the second application referred to, with the secrecy device in such a way that they are operated simultaneously c. e. when the plugs are up, or a connection is made at any substation by the insertion of the connecting plug into the jack of a main line, the line in use signal is shown at the same time the secrecy device is operated, so that at all the other substations a line in use annunciatoris displayed; and such achange is effected in the apparatus that it is impossible for any other substation to connect with the said main line as their line terminal sockets are rendered inoperative.

In carrying out the invention, suitable call sendingand receivingappliancesare provided to be operated inconjunction with any member of a series of metallic circuits and associated therewith are disconnecting signals. The metallic or double conductor main circuit extending between a central station and a substation or a number of substations or in fact between any two stations is provided with suitable means for effecting the secrecy of the main lines when connected at any substation, and means in combination therewith 8c for indicating the lines which are in use or busy and those that are not; and with said main circuit or any number of such main circuits is associated a common source of electric current, for example a primary or storage battery which can be located either at the central station or at any suitable and convenient place. One of the poles of this source of electrical energy may be connected to earth, and the other is extended by a supply con- 0 ductor to the several substations, entering these by branches which, when applied, unite with the center of the telephone coil or helix. The main circuit is normally open at the substations, but has plug socket or spring jack 5'. branch terminals adapted to receive looping and connecting plugs which are respectively the terminals of the telephone loop extending from its coil, and which, when thrust into their sockets, thereby close the said circuit [00 through the telephone helix; the telephone is thus included in the main circuits operatively and in such a way as to be fully responsive to currents circulating therein.

While there are many ways which we could employ to effect the secrecy of a main line telephone conductor, we prefer to employ electromagnetic apparatus in an earth branch from each main line at each substation connected to the said main line; the electro magnet has an armature, connected to which is an arm having upon its end aterminal piece, which is located just inside of a plug hole so that upon its insertion the plug will pass over the said terminal piece and prevent it from rising, at the same time making electric contact therewith. At the outside of the plug socket are two pins, one on each side thereof, forming branch terminals from either side of the main metallic circuit. The frame of the electro-magnet is connected to one side of the coil of the substation telephone, while the other side of the coil ends in a spring on the line connecting, plug. The plug is composed of a body of insulating material into which a metal spindle is inserted centrally at one end, and on either side thereof are inserted springs, one of which is connected to the central spindle, the other being connected, as aforesaid, by a wire loop to one side of the telephone coil, the center of which is connected to the supply conductor. The same source of electric current, used to call the central office, operates these electro magnets, and when a line is in use, 7'. 6. when the connecting plug atany substation is in a socket, thus closing the circuit at that point of any main line, all the electro-magnets legged or branched onto the line at any substation through which it passes have their armatures attracted (excepting the electro magnet at the substation where the plug is inserted, its armature is held from moving by the spindle of the plug) and the terminal ends of their levers are brought to a position to prevent a line plug at any other such substation being inserted in a jack branching from this main line; or the levers are brought to such a position that if the plug is inserted, it cannot make the electrical contact or continuity with the armature lever, necessary to closethe circuit through the metal frame of the electromagnet.

' We combine the line in use or busy indicator with the secrecy apparatus, and

preferably attach to vthe armature lover of the electro magnets an arm, bearing on its end a target which is divided into two parts, by different colored paints or otherwise: opposite the target is an opening in the frame of the box or case which incloses the apparatus, as described in the second application hereinbefore referred to. When the line is inuse at any substation and the armature lever is attracted to block the line at all other substations simultaneously therewith the line in use target is displayed. If the line is free, the circuit is open and the source of electricity cut off, the armatures of the electro magnets are unattracted and consequently none of the sockets are blocked and the line not in use target is displayed. The main circuit is a double conductor or metallic circuit and at the central station has a branch to earth including an electro-magnetic call annunciator common to all of the substations connected to the said main circuit.

Figure 1 is a diagram of a general system with which the invention may be associated. Fig. 2 is a diagram of one main circuit illustrating the invention. Fig. 3 is a side view partly in section of the combined electro-magnetic and secrecy apparatus shown connected in circuit in Fig. 2 with a connecting plug, and Fig. 4 is an alternative device, with its connecting plug.

In Fig. 1 is shown the general arrangement of a combination line system in association with which the invention maybe conveniently operated. G represents a central or end station for a number of metallic or double conductor circuits L, L and U. S, S and S represent out, or substations into which the said circuits enter by paired branches d, d 61 the several pairs terminating respectively in springjack or other plug socketsj,j and 3' Thus the two conductors a, a b, b and c, c of the several main circuits L, L and L lead into all of the sub stations normally connected with such circuits by multiple are or parallel branches, which, so far as this invention is concerned, are normally open or discontinuous, while at the end station 0 the two conductors of each main circuit are joined through the coils of suitable call receiving devices '0, o and c, and are furthermore provided with springjack connections 3, 3 .9 whereby central station appliances may be connected by the use of intermediate or linking conducting devices of any ordinary or well known character.

Fig. 2 indicates the mode in which our invention will be preferably carried out. L represents one of the double conductor circuits, and a and a are the direct and return conductors thereof, provided at the central or end station G with connecting branches 4 and 5, leading to contacts in spring jacks s. A differentially wound annunciator dropv is connected between the two main conductors.

and the earth branch 3; and at the station S it is assumed that the telephone T has been connected with the circuit and that the metallic circuit by such a connection has been closed through the telephone coils or helices 15, F. A source of electricity, shown as a battery B, is located at the central station 0, or at any other suitable and convenient place, and has one of its poles earthed, while the other connects with a call current supply conductor D which may form an extra member of-the group of line conductors and passes to the several substations of the system, abranch being led from it. into each, which branch is IIO permanently united to the telephone helix at a point e at the center thereof; or if the said telephones have two distinct helices, is serially connected at a point between them.

A at substations S and S represents the electro-magnetic secrecy device or apparatus, legged or branched from one side of the main circuit L by wires 00 and y respectively to ground. Its construction is more clearly shown in Fig. 3. 1, is the helix or coil of the electro-magnet, 2 is the armature therefor pivoted at points 6; attached to the armature is a lever 8 extending to the opposite end of the helix. and having a terminal end inclined as shown. 3 is a block of insulating material forming a side of a case to the back of which the helix 1 is secured; 16 is a hole through the block 3, the lower side of which is on a level or a little below the uppersurface of the armature lever terminal 11; on either side of the hole are metal pins 15 and 14. secured to the block 3. These are terminals of branches 12 and 13 from the respective sides a and a of the main line L. The plug P is composed of an insulating base or handle 19. Projecting from its center at one end is a metal spindle 18; and on either side thereof inserted in said handle, are metal springs 21 and 22, one of which 21 is connected to the spindle 18. The said supply circuit D is normally open, and the armatures 2 of the several electro magnets are normally retracted; but, when the plug P is inserted, as shown at substation S, the circuit is closed and the telephone there is connected with the main circuit; the armatures 2 are attracted at all of the substations, except the one at which the plug is inserted and the lever terminalsll at said substations block the holes 16 to prevent a plug from be ing inserted; or prevent the plug from makin g electrical contact with the said terminals, and the said terminal sockets are rendered inoperative. .When a plug is so inserted, its spindle 18 enters the hole 16 and strikes the end or terminal 11 of the armature lever 2, and passes in over the terminal, making an electrical contact and continuity therewith. The springs 21 and 22slide onto and make contact with the pins 14- and 15 respectively; thus closing a circuit from earth at central station battery B, supply and independent conductor D, to the point e. in the telephone coils where it divides, branching through wire 20 to the metal frame of the electro magnet, and by armature lever 8, its terminal 11 to spindle 18 of the plug P, and thence to its connected spring 21, pin 14, branch 13 to one side, a, of main line L; the other branch from thetelephoneis by wire 19 to spring 22 of plug P, pin 15, branch 12, to other side-a of main line L, both. sides of which unite at the central station through the call annunciator o and branch wire 3 tothe other pole of battery B or to earth. A portion of the current leaks by legs or branches or, y to earth through the helices of the electro magnets A at each substation, operating their armatures, asde;

scribed. We have shown theelectro-magnets of the secrecy devices as in a branch from side a of the main circuit at substation S, and in a branch from or of the said circuit at substation S in alternation, to properly balance .to block the plug hole 16, so that the plug could not be inserted sufficiently to connect its springs 21 and 22 with their .pins 14 and .15. Theplug shown here is of a simple character each spring connects directly to either. side of ,the telephone terminals, and there is no circuit through the metal parts of the electro magnet when it is in the socket.

We combinethe line in use indicator or annunciator with the electro magnetic secrecy apparatus, in the following way. In both of the devices, shown in Figs. 3 and 4, are shown an arm attached to the armature lever near its end brought out so as to come opposite an orifice 17 in the block 3; upon the end of the arm is a target 7 divided into two parts by different colored paint, or by any other suitable manner. When in its normal position, shown in Figs. 3 and 4, the upper part of the target 7 shows at the orifice 17, indicating that the line is not in use; while in the position shown at substation S Fig. 2, the lower part of the target is displayed at the opening 17 indicating that the line is in use. When the circuit is closed, as described, by the insertion of the plug P into a socket, the line'in'use annunciator is set or indicated simultaneously with the blocking of the plug hole or socket, and by the same act; .and simultaneously therewith the calling annunciator U at the centralstation which is common to all the substations in the main line, is caused to indicate that a call'has been made. And, while the telephone loop is :thus connected by its plug terminal with the armaturelever terminal, the electro magnetic secrecy apparatus, acts as a line continuity controllingvdevice in that the said lever terminal not onlyis caused topress against the spindle of. the plug and maintain the line intact while it is inserted, but. at the same time the operation of the said device, as aforesaid, at the other substations renders it impossible for alooping plugto be inserted in anyof the line sockets. there, to effect a connection.

Having nowfully described the invention,-

stations .and provided at the said substations I with fplug socket terminals; a secrecyidevice or apparatus connected with said circuit at.

each substation; a suitably located battery or equivalent source of electricity; an earth branch conductor including the said source of current, provided with connecting plug terminals adapted to be inserted in the said plug sockets, and thereby to simultaneously close the said main circuit, and the earth branch circuit including the source of electricity and to operate the said secrecy device, substantially as described.

2. The combination of a main double conductor telephone circuit extending between an end or central station and a series ofsubstations and provided at the-said substations with plug socket terminals; a secrecy device or apparatus, and a line in use indicator, connected with said circuit at eachsubstations; a suitably located battery or equivalent source I of electricity; an earth branch conductor i-ncluding the said source of current, provided with connecting plug terminals adapted to be inserted in the said plug sockets, and thereby to simultaneously close the said main circuit and the earth branch circuit including the source of electricity for the purposes described.

3. The combination of a main double conductor telephone circuit extending between an end or central station and a series of substations and provided at the said substations l with plug socket terminals; a secrecy device inserted in the said plug sockets and thereby to simultaneously close the said main circuit,

and the earth branch circuit including the source of electricity, for the purpose described.

4. The combination of a main double conductor telepb onecircuit, extendingfrom a terminal station to two substations and provided at the said substations with plug socket terminals; a secrecy device or apparatus included in an earth branch of said circuit at each of said substations; a telephone at the 1 substations; a suitably located battery or equivalent source of current; an earth branch 5 conductor extending from the said terminal station to the substations including the source 1 of current, and branching to the helices of the said telephones; and connecting plug terminals for the helices of the said telephones 1 adapted to be inserted in the said plug sockets and therebyto simultaneously close the main circuit and the earth branch circuit for the purposes described.

5. The combination of a main double con- 1 ductor telephone circuit extending between a terminal and two or more substations; a secrecy device or apparatus connected with said circuit or branches thereof at all of said substations; an independent earth branch extending from said terminal station to all of said substations, normally disconnected from said main circuit, and including an electrical generator; and means for closing the earth branch and thereby the generator circuit throughthe double conductor'circuit whereby the closure of the generator circuit is enabled to block or render inoperative the line terminal sockets of the said main circuit, at all of the other substations, substantially as de scribed.

6. The combination of a main double conductor telephone circuit extending froma central station to a number of substations and provided at each substation with plug socket branch terminals united respectively to the conductors of said circuit, secrecy devices or apparatus connected with said circuit, one at each substation; an electric generator such as a battery, common to all of the substations located at any desired point; an earth branch conductor including the said source of current, extending to each substation and provided with connecting plug terminals branched to each substation, adapted to be inserted in either of the plug sockets thereof, and thereby to simultaneously close the main circuit, and the earth branch circuit includingthe source of current, and also to simultaneously render inoperative the line terminal sockets at all of the other substations, substantially as described.

7. The combination of a main telephone circuit extending betweenan end or central station and aseries of substations and provided at the said substations with plug socket terminals; a combined secrecy device and line in use annun ciator connected with said main circuit at each substation; a suitably located battery or equivalent source of electricity; an earth branch conductor including the said source of current, provided with connecting terminals adapted to make connection with the said plug sockets and thereby to simultaneously close the said main circuit and the earth branch circuit including the source of electricity and to simultaneously actuate the said secrecy devices and the line in use annunciators to respectively render inoperative the line terminal sockets, and to indicate line in use at the said substations.

8. The combination of a double wire telephone circuit extending betweena central station and a series of substations, provided at each station with branch terminal connection devices, and with earth branches including electro-magnets; with atelephone loop at each station, having plug terminals to fit said connection devices, and thereupon to close said circuit through the telephone; a supply conductor extending from earth through a source of electricity and connected to the center of said loop whereby current may be directed over both conductors of the main circuit and their respective earth branches; and a continuity controlling device associated with each connection device and itself controlled bythe the'said electro-magn'et is excited by the in station, saidplugs being adapted to-fit said sertion of a plug at'any other substation, and the consequent flow of current through its containing earth branch and to thereby prevent the establishment'of a connection between the main circuit and the telephone loop at any station during the pendency of a similar connection at any other station.

9. The combination of a double wire telephone main circuit extending betweena central station and a series of substations, provided at each substation with branch'tei'rni} 'nal connection plug sockets, and with an earth branch including an electromagnetl; atelephone loop with plug terminals at each subsockets and to close said main circuit through the telephone included in said loop;-' a current supply conductor extending fromearth through a source of electrical energ to a permanent'connection at the center of said telephone loop, and adapted to close the circuit of said source through both conductors of said main circuit and their earth'branches and to excite the magnets thereof; a circuit controlling device and'a line condition indicating device at each. substation, both controlled by the earth branch electro-magnets of said substation and adapted to become operative upon tral station and a series of substations, providedat each substationfwith branch terminal plug sockets, and an earth branch including an electro-magnet, and at the central station with a permanent earth branch, and an annunciator included therein; a telephone loop with plug terminals at each substation, said plugs being adapted to fit said sockets and to close'said main circuit through the telephone included in said loop; a current supply conductor extending from-earth through a source of electrical energy to a permanent connection with said loop at the center of the helix of said telephone; and arranged to close the circuit of said source through both condoctors of said main circuit, and their-substation and central'station earthbranches and to excite the magnets thereofgand independent circuit controlling and line condition indicating devices at each substation controlled by the earth branch 'electromagnet of said substation, adaptedto become operative upon the establishment'ot a connection between the telephone loop-and main circuit at any other substatiomand thereupon to indi cate such'connection, and prevent interruptions-thereof,-substantially as described. In testimony whereof I-have signed my name to this specification, inthe presence of two subscribing witnesses, this 25th dayof rem-wmisss.

H v h SHERWOOD J. LARNED.

Witnesses: I

FRED GERLACK, ALBERTAADAMIGK. In testimony whereof I have signed my name to this specification; in the presence of two subscribing witnesses, this 6th day of March,1893; i

FRANK A. PIOKERNELL."

Witnesses:

RJJ, MORGAN, CHARLES D M. COLE.- 

